Neurogenic cells inhibit the differentiation of cardiogenic cells.

In this study, we present evidence that neurogenic cells inhibit the differentiation of cardiogenic cells. When cells of the entire area pellucida at stage 5 were dissociated and reaggregated, the aggregates differentiated into neural tissues and other structures of any germ layer origin, except for heart tissues, despite the fact that the cardiogenic cells are already committed to differentiate. The phenomenon also occurs from stages 6 to 8, during which cells are in a higher state of commitment. Using combinations of different regions of the area pellucida, it was confirmed that neurogenic cells are responsible for the inhibition of cardiogenic cell differentiation. The inhibition is not species-specific because quail and chick neurogenic cells inhibit each other's cardiogenic cell differentiation. Direct contact between cardiogenic and neurogenic cells seems to be necessary for inhibition because cardiogenic cell differentiation takes place if cardiogenic and neurogenic cells are separated by a porous membrane. Dissociated neural tubes from early stages, but not dissociated telencephalon from 2-day-old chicks, also inhibit cardiogenic cell differentiation. These results suggest that neurogenic cells may sequester molecules necessary for the differentiation of cardiogenic cells rather than produce inhibitory molecules.